The present invention concerns a vacuum manipulator comprising an elongated body with two segments of longitudinal ducts, one of which opens at one end of said body and is intended to be connected to a suction source and the other, one of which is intended to be fitted with a suction nozzle. The internal ends of these duct segments communicate laterally via respective holes with the bottom of the longitudinal guide channel. The guide channel constitutes the seat of a spool valve mounted in a longitudinal fashion and sliding in this guide channel.
The U.S. Pat. No. -A-3,843,183 patent already describes such an instrument equipped with a sliding spool valve. The problem which exists with such a valve is that of the air tightness existing between the bottom of the guide channel, which constitutes the seat of the valve, and the surface of this valve in contact with this valve. When a vacuum is applied at the level of the hole which puts the seat of the valve in communication with the suction source, the valve is applied against said seat with a force corresponding to the vacuum. Of course, the specific pressure is all the higher than the bearing surface is smaller; a lower limit should not, however, be exceeded to avoid the development of leaks. Furthermore, the length and the width of the valve should be sufficient to ensure the guide and stability of this sliding part. For reasons of weight and price, the body of this instrument as well as the spool valve are preferably made out of molded plastic. It results from these various data that it is practically extremely difficult, if not impossible, to manufacture a valve long and wide enough and to obtain simultaneously a good airtightness between said valve and its seat, since the specific pressure is too low and it is impossible to ensure a perfect contact over the whole surface especially with plastic parts.
The goal of this invention is to remedy, partly at least, the hereabove-mentioned disadvantages by ensuring at once a good guide function and a good air tightness of the spool valve.
The instrument, according to the invention, is of a simple construction, of a reliable operation and an easy manipulation. Many other advantages will appear during the description accompanying the appended drawing which illustrates, schematically and as an example, a form of execution of the instrument which is the object of the present invention.